1. Field of the Invention
An apparatus consistent with the present invention relates to a frequency band of a communication system and, more particularly, to a method of transmitting and receiving data using a multi-band.
2. Description of the Related Art
A communication system generally uses frequency of a predetermined band for data transmission. The data used in such communication are mainly classified as circuit data or packet data. The circuit data requires real-time transmission and reception such as audio signals. The packet data have a certain amount of data, such as packet information, and do not necessarily require real-time data transmission. The frequency band for the circuit data is usually narrow, while the frequency band for the packet data is relatively wide.
When the amount of data for transmission increases, the frequency band also increases. Hereinbelow, the relatively wider frequency band is called ‘Ultra Wide Band (UWB)’. The UWB is divided into a plurality of sub-frequency bands. The communication system transmits data using the plurality of sub-frequency bands at a predetermined time, and is capable of transmitting a considerable amount of data during the predetermined time period. The communication system selects one among the plurality of sub-frequency bands during the predetermined time period, and transmits data using the selected sub-frequency band. Therefore, data security can be provided. In other words, because the plurality of sub-frequency bands are sequentially used, data security can be guaranteed.
FIG. 1 shows the structure of a currently-suggested UWB. As shown, the currently-suggested UWB uses frequency bands from 3432 MHz to 10032 MHz. The frequency bands of the UWB are mainly grouped into 4 groups, i.e., Groups A, B, C and D. Group A consists of 3 sub-frequency bands, and Group B consists of 2 sub-frequency bands. Group C consists of 4 sub-frequency bands, and Group D consists of 4 sub-frequency bands.
More specifically, there are frequencies of 3432 MHz, 3960 MHz and 4488 GHz at 3 sub-frequency bands of Group A, and there are 5016 MHz and 5808 MHz at the 2 sub-frequency bands of Group B. Group C consists of 4 frequencies of 6336 MHz, 6864 MHz, 7392 MHz and 7920 MHz, and Group D consists of 4 frequencies of 8448 MHz, 8976 MHz, 9504 MHz and 10032 MHz. The sub-frequency bands of Group B overlap with the frequency bands currently used in wireless LAN, and it is almost impossible to use the sub-frequency bands of Group D with currently-available technology. Accordingly, the use of sub-frequency bands of Groups A and C is mainly discussed.
In order to use the 3 sub-frequency bands of Group A and the 4 sub-frequency bands of Group C, 7 reference signals need be generated. In other words, a structure is required to generate 7 reference signals for the use of 3 the sub-frequency bands of Group A and the 4 sub-frequency bands of Group C.
The communication system transmits data using reference signals, and generally, the 7 reference signals are generated by a local oscillator. The local oscillator will now be explained briefly below.
FIG. 2 shows an oscillator to generate 7 reference signals. As shown, there are 7 local oscillators for the generation of the 7 reference signals. In other words, one local oscillator is' required to generate one reference signal. A phase locked loop (PLL) operates to stabilize the frequency of the reference signals, which are generated by the local oscillators. Accordingly, each local oscillator has a corresponding PLL. The process of generating the 7 reference signals will be described below with reference to FIG. 2.
A first local oscillator 200 generates a reference signal at a frequency of 3432 MHz, and a second local oscillator 202 generates a reference signal at a frequency of 3960 MHz. A third local oscillator 204 generates a reference signal at a frequency of 7920 MHz. A first PLL 210 stabilizes the frequency of the reference signal generated at the first local generator 200 and transmits it to a selector 220. A second PLL 212 stabilizes the frequency of the reference signal generated at the second local oscillator 202 and transmits it to the selector 220. A third PLL 214 stabilizes the reference signal generated at the third local generator 204 and transmits it to the selector 220. In accordance with a control signal, the selector 220 selects one among the stabilized reference signals and outputs the selected reference signal. The reference signal outputted from the selector 220 is combined with data and transmitted to the receiver.
As shown in FIG. 2, in order to generate 7 reference signals, 7 local oscillators together with 7 corresponding PLLs are required. The problem is that the local oscillators and the PLLs consume a good deal of energy. Additionally, the local generators and PLLs increase the overall volume of the system. Therefore, an improved method to resolve these problems is required.